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Abstract: Structure elucidation plays a critical role across the landscape of medicinal chemistry, including medicinal inorganic chemistry. Herein, we discuss the importance of structure elucidation in drug development and then provide three vignettes that capture key instances of its relevance in the development of biologically active inorganic compounds. In the first, we describe the exploration of the biological activity of the trinuclear Ru compound called ruthenium red and the realization that this activity derived from a dinuclear impurity. We next explore the development of Au‐based antitubercular and antiarthritic drugs, which features a key step whereby ligands were discovered to bind to Au through S atoms. The third exposition traces the development of As‐based antiparasitic drugs, a key step of which was the realization that the reaction of arsenic acid and aniline does not produce an anilide of arsenic acid, as originally thought, but rather an amino arsonic acid. These case studies provide the motivation for an outlook in which the development of Sb‐based antiparasitic drugs is described. Although antileishmanial pentavalent antimonial drugs remain in widespread use to this day, their chemical structures remain unknown.

Ruthenium‐indane complex, fac‐[Ru(NCMe)3(CO)2(InCl3)] 1Cl reacted with 0.5 equiv. of dppe/dppp to afford dinuclear ruthenium‐indane complexes linked by diphosphine ligand, [{Ru(NCMe)2(CO)2(InCl3)}2{μ2‐Ph2P(CH2)nPPh2}] (n=2: 3, 3: 4). On the other hand, the reaction of fac‐[Ru(NCMe)3(CO)2(InCl3)] 1Cl with 1 equiv. of dppp afforded the corresponding chelate ruthenium(0) indane complex, [Ru(NCMe)(CO)2(InCl3)(dppp)] 5. In the case of dppm, a chelate complex [Ru(NCMe)(CO)2(InCl3)(dppm)] 6 was formed via the dinuclear Ru complex [{Ru(NCMe)2(CO)2(InCl3)}2(μ2‐dppm)]. Complexes 1Cl, 5, and 6 showed a catalytic activity for double‐hydrosilylation of MeCN. Complexes 3–6 were fully characterized using NMR measurements, elemental analyses, and the structures of 1Cl, 3, 5, and 6 were determined by X‐ray crystallography. [ABSTRACT FROM AUTHOR]

The catalytic hydrogenation of CO2 to formate was achieved using the previously reported dichloro(η6‐p‐cymene){diphenyl(3‐methyl‐2‐indolyl)phosphine}ruthenium (1) as a catalyst under mild conditions. In this complex, the phosphorus‐based ligand adopts a κ1‐P coordination mode. The catalytic activity was achieved in the presence of DBU as a base providing a TONmax value of 3,800. In order to explore potential transformations occurring within the catalytic reactions, a series of stoichiometric tests were performed. Complex 1 was reacted with DBU to form chloro(η6‐p‐cymene){diphenyl(3‐methyl‐2‐indolide)phosphine}ruthenium (2). Structural characterization of complex 2 confirmed a κ2‐P,N coordination mode for the ligand resulting in a four membered metallacycle. Reaction of 2 with H2 led to the formation of hydrochloro(η6‐p‐cymene){diphenyl(3‐methyl‐indolyl)phosphine}ruthenium (3), albeit not with a clean conversion. This is the product resulting from the formal addition of hydrogen across the Ru−N bond of the metallacycle. Complex 3 was also synthesized via an alternative route involving the reaction of complex 1 with Me2NH • BH3 as a means of converting Ru−Cl to Ru−H [ABSTRACT FROM AUTHOR]

A Grubbs‐type ruthenium complex bearing a tridentate anionic bisfluoroalkoxy‐carbene was synthesised and fully characterised. Under standard conditions, it proved to be inactive in olefin metathesis reactions, but the addition of HCl triggers its activity and allows the synthesis of a series of cyclic olefins and ethers as well as a stereoregular polynorbornene with an unexpectedly high content of trans‐configured double bonds, as found in commercially available polynorbornene (Norsorex®). Detailed structural studies and DFT calculations showed that the complex enters the catalytic cycle, but instead of performing a full turnover, it is caught as a stable intermediate that does not undergo further reactions. The addition of HCl causes dissociation of the fluoroalkoxy units, resulting in a compound that behaves similarly to standard Grubbs‐type complexes. To further understand this phenomenon, the corresponding Hoveyda‐Grubbs complex was also obtained and studied in detail; due to the absence of the phosphine ligand, its behaviour was different from that of its Grubbs‐type counterpart. [ABSTRACT FROM AUTHOR]

Nitrosyl ruthenium complexes have emerged as promising platforms for the controlled delivery of nitric oxide (NO) and nitroxyl (HNO), both of which possess significant therapeutic implications. Considering this scenario, we synthesized and characterized the metal complex cis‐[RuNO(phen)2(2MIM)]3+ and its precursors, where phen and 2MIM correspond to 1,10‐phenantroline and 2‐methylimidazole, respectively. Comprehensive structural elucidation was undertaken using a combination of spectroscopic and electrochemical methodologies, including XANES/EXAFS experiments. This structural data was further validated through DFT computational analyses. We demonstrated that such compound can release NO and HNO in the presence of thiol‐based substrates. Not only this, but the same metal complex can also delivery nitric oxide under irradiation with visible light (λ=460 nm). The nitrosyl complex and its derivatives displayed marked vasodilatory capabilities as evidenced in assays involving isolated rat aorta rings. They also exhibited commendable antioxidant activity in free radical scavenging assays. Collectively, based on these data, this nitrosyl ruthenium compound is a potential therapeutic candidate, especially in the field of cardiovascular pathology like atherosclerosis, thereby deserving further in‐depth investigations. [ABSTRACT FROM AUTHOR]

Ru(II)‐arene compounds are being investigated as anticancer agents due to the biocompatibility of ruthenium and their structural diversity. Two newly synthesized Ru(II) complexes, [RuCl(η6‐p‐cymene)(3‐DNPH)] (chlorido(η6‐p‐cymene)(3‐nitrophenylhydrazine‐k2N,N′)ruthenium(II)) (1) and [RuCl(η6‐p‐cymene)(3‐CNPH)] (chlorido(3‐chlorophenylhydrazine‐k2N,N′)(η6‐p‐cymene)ruthenium(II)) (2), are experimentally (IR, NMR) and theoretically (B3LYP/6‐31+G(d,p)(H,C,N,Cl)/LanL2DZ(Ru)) characterized. Experimental and theoretical values of 1H and 13C chemical shifts and position of the most intense vibrational bands showed high correlation coefficients and low mean absolute errors, proving the predicted structure and applicability of the selected level of theory. Cell viability studies performed on MDA‐MB‐468, BT‐474, and PC3 cells using MTT and CV assay indicated the activity of the second complex similar to the activity of cisplatin towards BT‐474 breast cancer cells. The spectrofluorimetric measurements of Bovine Serum Albumin showed the binding process's spontaneity of complexes and protein, with a binding energy of around −30 kJ mol−1. Detailed molecular docking analysis allowed the elucidation of the binding mechanism through specific intermolecular interactions. Both compounds showed a higher affinity towards BSA than naproxen and cisplatin. Molecular docking simulations proved the spontaneity of the complexes binding to DNA. Based on these promising results, further biological examinations of these compounds are advised. [ABSTRACT FROM AUTHOR]

The article dealt with the structurally validated L2− (H2L=epindolidione=5,11‐dihydroquinolino[3,2‐b]quinoline‐6,12‐dione, a heteroatom‐modified tetracene and a structural isomer of indigo dye) bridged {(acac)2RuIII}2(μ‐L2−) 1/2 (S=1, acac=acetylacetonate) and [{(bpy)2OsII}2(μ‐L2−)](ClO4)2 [3](ClO4)2/[(pap)2OsII}2(μ‐L2−)](ClO4)2 [4](ClO4)2 (S=0, bpy=2,2′‐bipyridine, pap=2‐phenylazopyridine). 1/2 and [3](ClO4)2/[4](ClO4)2 with a metal‐metal separation of ≈7 Å stabilized selectively in meso(ΔΛ)/rac(ΔΔ/ΛΛ) and meso diastereomeric forms, respectively, in spite of calculated minor difference in energy between the diastereomers in each case. Though 2, [3](ClO4)2/[4](ClO4)2) exhibited intermolecular π–π interactions, no such non‐covalent interaction was perceived in 1. RuIIIRuIII derived 1/2 (S=1, 2.63/2.57 μB at 300 K) attributed to non‐interacting two Ru(III) (S=1/2) spins with an intermolecular through space weak antiferromagnetic exchange interaction below 12 K and its variable temperature 1H NMR revealed Fermi and pseudo‐contact shifts. Multiple redox steps of the complexes varied as a function of metal ion (Ru versus Os), its oxidation state (III versus II) and ancillary ligand (acac versus bpy versus pap). A collective consideration of DFT calculated MOs and Mulliken spin densities suggested delicate electronic forms along the redox chain due to the participation of bridge largely in the oxidation processes as a consequence of its redox non‐innocent feature. Reductions were however mostly centered around the metal (RuIII to RuII) and ancillary ligands (bpy/pap) in 1/2 and 32+/42+, respectively. 1n/2n, [3]2+/[4]2+ displayed mixed metal/ligand based weak low‐energy (800‐1400 nm) transitions in addition to intense visible bands as corroborated by TD‐DFT calculations. [ABSTRACT FROM AUTHOR]

Ligand design is crucial for the design of robust and efficient molecular water oxidation catalysts (WOCs) based on metal complexes. Herein we report the water oxidation studies of a series of Ru WOCs bearing bipyridine dialkoxide ligands with different substituents. Combined with density functional theory (DFT) calculations, the proposed water oxidation mechanism is bimolecular coupling (I2M) of two seven‐coordinate (CN7) Ru=O species. The use of bulky phenyl groups on the planar alkoxide ligand helps to stabilize the high oxidation CN7 intermediates, without loss of ligand flexibility. This strategy may be useful for the design of other active WOCs. [ABSTRACT FROM AUTHOR]

The development of efficient catalysts for the dehydrogenation of formic acid (FA) through molecular level control and precise regulation remains challenging. Herein, we report the newly developed complexes of iridium and ruthenium with nitrogen‐rich ligand for aqueous FA dehydrogenation. The Cp*Ir complex 1 (Cp*=cyclopentadienyl) and Ru(p‐cym) complex 2 (p‐cym=p‐Cymene) were synthesized and fully characterized. The single crystal structures of these complexes have a typical piano‐stool structure. A turnover frequency of 12468 h−1 was achieved for FA dehydrogenation at 90 °C by using complex 1 bearing 3,3'‐diamino‐5,5'‐bis(1H‐1,2,4‐triazole) (DABT). The effects of pH, temperature, concentration of formic acid and amount of catalyst on the reaction kinetics were studied in detail. Kinetic isotope effect (KIE) experiments and 1H NMR detection of reaction revealed that a plausible mechanism involves the decarboxylation of formate and the formation of H2. More importantly, the influence of H2O and H+ was involved in the rate‐determining step. This study demonstrated the effectiveness of nitrogen‐rich ligand for FA dehydrogenation, which would contribute to the development of new and effective hydrogen release systems. [ABSTRACT FROM AUTHOR]

The thioether‐group‐containing SNS‐type pincer complex [({EtSCH2CH2}2NH)RuCl(H)(PPh3)] (2) exists in three different diastereomers (2 a–c). The molecular structures obtained from single crystal X‐Ray diffraction studies of all three isomers reveal a difference in the relative orientation of the respective EtS‐groups, while other commonly observed diastereomers as the result of cis‐/trans‐ or fac‐/mer‐isomerism are not observed. Chemical exchange between the three diastereomers 2 a–c was discovered by phase‐sensitive 1H and 31P NOESY NMR spectroscopy, and further quantified by line shape analysis of 1H NMR spectra. The experimentally derived averaged Gibbs energies of activation for the interconversion of the isomers (65–70 kJ/mol) are in good agreement with the results obtained from DFT calculations, which suggest an inversion of the ligating sulfur atoms, although a dissociative pathway for the configurational inversion can be competitive. [ABSTRACT FROM AUTHOR]

Building upon our earlier results on the chemistry of nido‐1,2‐[(Cp*RuH)2B3H7] (Cp*=ɳ5‐C5Me5) (nido‐1) with different transition metal carbonyls, we continued to investigate the reactivity with group 7 metal carbonyls under photolytic condition. Photolysis of nido‐1 with [Mn2(CO)10] led to the isolation of a trimetallic [(Cp*Ru)2{Mn(CO)3}(μ‐H)(μ‐CO)3(μ3‐BH)] (2) cluster with a triply bridging borylene moiety. Cluster 2 is a rare example of a tetrahedral cluster having hydrido(hydroborylene) moiety. In an attempt to synthesize the Re analogue of 2, a similar reaction was carried out with [Re2(CO)10] that yielded the trimetallic [(Cp*Ru)2{Re(CO)3}(μ‐H)(μ‐CO)3(μ3‐BH)] (3) cluster having a triply bridging borylene unit. Along with 3, a trimetallic square pyramid cluster [(Cp*Ru)2{Re(CO)3}(μ‐H)2(μ‐CO)(μ3,ɳ2‐B2H5)] (4), and heterotrimetallic hydride clusters [{Cp*Ru(CO)2}‐{Re(CO)4}2(μ‐H)] (5) and [{Cp*Ru(CO)}{Re(CO)4}2(μ‐H)3] (6) were isolated. Cluster 4 is a unique example of a M2M′B2 cluster having diboron capped Ru2Re‐triangle. The hydride clusters 5 and 6 have triangular RuRe2 frameworks with one and three μ‐Hs respectively. All the clusters have been characterized by using mass spectrometry, 1H, 11B{1H}, 13C{1H} NMR and IR spectroscopies analyses and the structures of clusters 2–6 have been unambiguously established by XRD analyses. Furthermore, to understand the electronic, structural, and bonding features of the synthesized metal‐rich clusters, DFT calculations have been performed. [ABSTRACT FROM AUTHOR]

We report heteroleptic ruthenium complexes of terpyridine (tpy) ligands with directly linked carboxylic acid anchors. These complexes feature methyl or methoxy‐substituted 4′−Phtpy as donor ligands. We prepared these heteroleptic complexes from the ruthenium (II) precursor via a milder route to preclude the homoleptic complex formation. The donor−acceptor arrangement of tpy ligands in these ruthenium complexes renders visible light absorption giving metal and ligand‐to‐ligand charge transfer excitations at c.a. 490 nm. We evaluate the effect of the tpy donor substituents on the light‐harvesting ability in Dye‐Sensitized Solar Cells (DSSCs) and compare their photosensitizing ability with heteroleptic complexes bearing phenyl spacer at the acceptor end. Further, scrutinizing their photovoltaic performance, we studied their electron transfer kinetics in DSSCs using electrochemical impedance spectroscopy. This paper presents the structure‐photosensitization relationship of these heteroleptic ruthenium complexes through a combined experimental and computational approach. [ABSTRACT FROM AUTHOR]

A catalytic system for the direct β‐alkylation of secondary alcohol with primary alcohol has been investigated. In this work, a series of cationic Ru(II)(η6‐p‐cymene) complexes with thioether‐functionalized N‐heterocyclic carbene ligands (imidazole‐based 1 a–l and benzimidazole‐based 2 a–e) have been successfully synthesized and evaluated as catalysts. This investigation shows that modifications in the ligand moiety (thioether group and/or NHC core) have a strong effect on both selectivity and reactivity. Imidazole‐based complex 1 c, with only 1 mol % of catalyst loading, displayed the best catalytic activity as well as the highest selectivity for the β‐alcohol up to 98 : 2 for this tandem borrowing hydrogen/aldol methodology. Applied to a wide range of substrates, β‐alkylated secondary alcohols have been obtained in moderate yields, but generally with complete conversion and very high selectivity. [ABSTRACT FROM AUTHOR]

A series of piano‐stool Ru−NHC (NHC=N‐heterocyclic carbene) complexes have been prepared and characterized. The NHC ligands used herein have varying wingtip groups, showing the impact of steric congestion on the selectivity for the catalytic dimerization of terminal alkynes. [ABSTRACT FROM AUTHOR]

Three Hoveyda‐Grubbs complexes supported by N‐(9‐alkylfluorenyl)imidazol‐2‐ylidene ligands (alkyl=methyl, ethyl or benzyl) have been synthesized. With the aim to generate chelating, cyclometalated (C,CNHC) ruthenium complexes for Z‐selective olefin metathesis, the C(sp3)‐H activation of the dangling alkyl group has been studied. While the methyl derivative leads to the expected cyclometalated complex, a C(sp2)‐H activation of the fluorenyl moiety and no evolution/transformation are observed for the ethyl and benzyl derivatives, respectively. Although highly fragile under catalytic conditions, the cyclometalated complex leads to Z/E stereoselectivity up to 94/6. An unprecedented insertion of the alkylidene moiety into the Ru‐CNHC bond leading to ruthenium N‐heterocyclic olefin complexes is also observed and supported by calculations of the corresponding reaction pathway. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of a new acetylene‐bridged triphosphine, ((phenylphosphanediyl)bis‐(ethyne‐2,1‐diyl))bis(diphenylphosphane) [PhP{C≡CPPh2}2] (2) and its coordination complexes of RuII, RhIII, CuI, PdII and PtII. The reaction of diethynylphenylphosphine [PhP{C≡CH}2] (1) with two equivalents of LiHMDS followed by the addition of PPh2Cl resulted in 2. Treatment of 2 with [Ru(η6‐p‐cymene)Cl2]2 and [RhCp*Cl2]2 in 1 : 1.5 molar ratios produced trinuclear complexes [{Ru(η6‐p‐cymene)Cl2}3{μ3‐PPh(C≡CPPh2)2}] (3) and [(RhCp*Cl2)3{μ3‐PPh(C≡CPPh2)2}] (4). The molecular structure of 3 was confirmed by single crystal X‐ray analysis. Treatment of 2 with M(COD)Cl2 (M=Pd, Pt) in 2 : 3 ratio afforded open book type complexes [(MCl2)3{μ3‐PPh(C≡CPPh2)}2] (5 M=Pd, 6 M=Pt). The reaction of 2 with CuI in 1 : 2 ratio afforded 1‐D coordination polymer [{Cu2(μ2‐I)2(CH3CN)}{PPh(C≡CPPh2)2}3{CuI}2] (7) containing [(CuI)2{μ2‐(P−C≡C−P)3}] cylindrical units. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of a new acetylene‐bridged triphosphine, ((phenylphosphanediyl)bis‐(ethyne‐2,1‐diyl))bis(diphenylphosphane) [PhP{C≡CPPh2}2] (2) and its coordination complexes of RuII, RhIII, CuI, PdII and PtII. The reaction of diethynylphenylphosphine [PhP{C≡CH}2] (1) with two equivalents of LiHMDS followed by the addition of PPh2Cl resulted in 2. Treatment of 2 with [Ru(η6‐p‐cymene)Cl2]2 and [RhCp*Cl2]2 in 1 : 1.5 molar ratios produced trinuclear complexes [{Ru(η6‐p‐cymene)Cl2}3{μ3‐PPh(C≡CPPh2)2}] (3) and [(RhCp*Cl2)3{μ3‐PPh(C≡CPPh2)2}] (4). The molecular structure of 3 was confirmed by single crystal X‐ray analysis. Treatment of 2 with M(COD)Cl2 (M=Pd, Pt) in 2 : 3 ratio afforded open book type complexes [(MCl2)3{μ3‐PPh(C≡CPPh2)}2] (5 M=Pd, 6 M=Pt). The reaction of 2 with CuI in 1 : 2 ratio afforded 1‐D coordination polymer [{Cu2(μ2‐I)2(CH3CN)}{PPh(C≡CPPh2)2}3{CuI}2] (7) containing [(CuI)2{μ2‐(P−C≡C−P)3}] cylindrical units. [ABSTRACT FROM AUTHOR]

While ruthenium(II) arene complexes have been widely investigated for their potential in catalytic transfer hydrogenation, studies on homologous compounds replacing the arene ligand with the six‐electron donor tris(1‐pyrazolyl)methane (tpm) are almost absent in the literature. The reactions of [RuCl(κ3‐tpm)(PPh3)2]Cl, 1, with a series of nitrogen ligands (L) proceeded with selective PPh3 mono‐substitution, affording the novel complexes [RuCl(κ3‐tpm)(PPh3)(L)]Cl (L=NCMe, 2; NCPh, 3; imidazole, 4) in almost quantitative yields. Products 2–4 were fully characterized by IR and multinuclear NMR spectroscopy, moreover the molecular structure of 4 was ascertained by single crystal X‐ray diffraction. Compounds 2–4 were evaluated as catalytic precursors in the transfer hydrogenation of a series of ketones with isopropanol as the hydrogen source, and 2 exhibited the highest activity. Extensive NMR experiments and DFT calculations allowed to elucidate the mechanism of the transfer hydrogenation process, suggesting the crucial role played by the tpm ligand, reversibly switching from tri‐ to bidentate coordination during the catalytic cycle. [ABSTRACT FROM AUTHOR]

A series of ruthenium bis(σ‐B−H) borate complexes 1–4 have been prepared by a salt‐elimination protocol using lithium monoaryl trihydroborates Li[ArBH3] (R=Ph, 3,5‐(CF3)2C6H3, o‐tol or Mes) and the corresponding metal halide Cp*Ru(PCy3)Cl. All of these bis(σ‐B−H) borate complexes are stable at room temperature and isolated in good yields (70–92 %). Additionally, treatment of 4 with the hydride abstracting agent B(C6F5)3 generated rare cationic bis(σ‐B−H) borane complex 5. Crystallographic characterization data are provided for 3 and 5. All these new complexes were fully characterized by multinuclear NMR spectroscopy and elemental analysis. [ABSTRACT FROM AUTHOR]

In this work, the anion‐responsive conduct of a Ru(II)‐bipyridine complex incorporating pyrazolyl‐bis (benzimidazole) ligand is thoroughly investigated in acetonitrile and water via absorption and emission spectroscopy as well as by square‐wave voltammetry (SWV). Substantial alteration of the photo‐redox behavior of the complex is observed in the presence of the selected anions. The free form of the complex exhibits emission indicating the "on‐state", while inclusion of anions leads to quenching of emission and represents the "off‐state". The restoration of the initial state of the complex is feasible in the presence of acid and the process is reversible and can be recycled. In essence, the complex functions as anion‐ and acid‐responsive molecular switches. Additionally, we applied herein neural network based deep learning methodologies, viz. Artificial Neural Networks (ANNs) and Adaptive Neuro‐Fuzzy Inference System (ANFIS)} for thorough analysis and fully understand the multi‐channel anion sensing behavior of the complex. [ABSTRACT FROM AUTHOR]

The reaction of [RuCl2(CO)3]2 and Te2Tpn2 (Tpn=thiophen‐2‐yl, C4H3S) in the absence of light resulted in the formation of cct‐[RuCl2(CO)2(TeTpn2)2] (1) [cis(Cl)‐cis(CO)‐trans(TeTpn2)] and TeTpn2 (2) together with the precipitation of tellurium. The complex 1 and the monotelluride 2 were characterized by NMR spectroscopy and single‐crystal X‐ray diffraction. The decomposition of Te2Tpn2 to TeTpn2 has been monitored by 125Te NMR spectroscopy and seemed to be faster than the ligand substitution in [RuCl2(CO)3]2 by TeTpn2. A catalytic cycle is proposed for the decomposition of Te2Tpn2 to TeTpn2 based on the PBE0‐D3/def2‐TZVP calculations. [ABSTRACT FROM AUTHOR]

Addition of an excess of ZnMe2 to a mixture of [Ru(PPh3)3HCl] and IMes (IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene) yields the bis‐cyclometallated complex, [Ru(IMes)"(PPh3)2] 2, together with the mono‐cyclometallated, Ru−Zn heterobimetallic complex [Ru(IMes)′(PPh3)2(ZnMe)] 3. Treatment of 2 with H2, PhSiH3 or pinacolborane yields the previously reported complex, [Ru(IMes)′(PPh3)2H] 1, the synthesis of which has been reinvestigated. Further studies of small molecule reactivity show that 1 adds H2 to give [Ru(IMes)(PPh3)2H4] 4, whilst 2 reacts with catecholborane to give [Ru(IMes‐Bcat)′(PPh3)2H] 5, in which (IMes‐Bcat)′ signifies a borylated NHC ligand that is singly‐metallated onto Ru. Treatment of 2 with CO gives the 18‐electron dicarbonyl product [Ru(IMes)"(PPh3)(CO)2] 6. Compounds 1–3, 5 and 6 have been structurally characterised. [ABSTRACT FROM AUTHOR]

Addition of an excess of ZnMe2 to a mixture of [Ru(PPh3)3HCl] and IMes (IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene) yields the bis‐cyclometallated complex, [Ru(IMes)"(PPh3)2] 2, together with the mono‐cyclometallated, Ru−Zn heterobimetallic complex [Ru(IMes)′(PPh3)2(ZnMe)] 3. Treatment of 2 with H2, PhSiH3 or pinacolborane yields the previously reported complex, [Ru(IMes)′(PPh3)2H] 1, the synthesis of which has been reinvestigated. Further studies of small molecule reactivity show that 1 adds H2 to give [Ru(IMes)(PPh3)2H4] 4, whilst 2 reacts with catecholborane to give [Ru(IMes‐Bcat)′(PPh3)2H] 5, in which (IMes‐Bcat)′ signifies a borylated NHC ligand that is singly‐metallated onto Ru. Treatment of 2 with CO gives the 18‐electron dicarbonyl product [Ru(IMes)"(PPh3)(CO)2] 6. Compounds 1–3, 5 and 6 have been structurally characterised. [ABSTRACT FROM AUTHOR]

[Ru(bpyPO3H2)(bpy)Cl]Cl (bpyPO3H2=6,6'‐bipyridin‐2‐yl)phosphonic acid) and [Ru(tpy)(MepyPO3H2)Cl]Cl (MepyPO3H2=(pyridin‐2‐ylmethyl)phosphonic acid) were synthesized and characterized spectroscopically and electrochemically. Each compound was found to exhibit proton‐coupled electron transfer (PCET). In the case of [Ru(bpyPO3H2)(bpy)Cl]Cl, a Ru(V/IV) couple was detected at 1.4 V vs. NHE. Each complex was tested for its ability to catalyze C−H bond oxidation using a variety of sacrificial oxidants, and it was found that under aqueous conditions [Ru(bpyPO3H2)(bpy)Cl]Cl oxidizes secondary C−H bonds using sodium periodate (NaIO4) as the primary oxidant. [ABSTRACT FROM AUTHOR]

We investigated the evolution of Ru clusters containing 1–4 atoms supported on graphene in CO atmosphere with extensive first principle‐based calculations. Exothermic CO adsorption induces gradual structure reorganization and change of the Ru−Ru, Ru‐graphene, and Ru‐CO interactions within these Ru carbonyls. The upper limits of CO on a surface of Ru cluster are 3, 6, 10 and 12 for Ru1, Ru2, Ru3 and Ru4, respectively. The further CO adsorption enhances steric hindrance at the Ru‐graphene interface that finally leads to release of undercoordinated Ru carbonyls into gas phase. Competing with the CO adsorption and sintering of Ru species for better thermostability, disintegration of multinuclear surface Ru carbonyls to atomically dispersed Ru species on graphene is still feasible. The current findings bring more insights into the evolution and interconversion of Ru carbonyls in a CO atmosphere and may help to understand the superior performance of heterogeneous transition metal catalysts in operation conditions. [ABSTRACT FROM AUTHOR]

Multinuclear porphyrin‐based ruthenium(II)‐NNNN complexes were efficiently assembled by means of coordinatively unsaturated 16‐electron mononuclear ruthenium(II)‐pyrazolyl‐imidazolyl‐pyridine complex, zinc(II) meso‐tetra(4‐pyridyl)‐porphyrin (ZnTPyP), and 4,4′‐linked bipyridines. The resultant multinuclear (Ru4 and Ru8) porphyrin‐based ruthenium(II)‐NNNN complexes exhibited exceptionally high catalytic activity at as low as 0.008 mol % Ru loading for the transfer hydrogenation reaction of ketones in refluxing 2‐propanol, reaching up to 99 % yields and 5.7×106 h−1 TOFs. [ABSTRACT FROM AUTHOR]

Aiming highly efficient conversion of greenhouse gas CO2 to cyclic carbonates, a biomass Ru(III) Schiff base complex catalyst (SalRu) was constructed by employing a derivative of Lignin degradation (5‐aldehyde vanillin). The SalRu catalyst had a remarkable conversion for epoxides into corresponding cyclic carbonates even at atmospheric pressure of CO2 without the presence of co‐catalyst. As the condition at 120 °C and 2 MPa CO2 the conversion reached to 94 % with selectivity at 99 % after 8 h. 32 % cyclic carbonate production was obtained even under 0.2 MPa CO2 pressure. The epoxide activation and ring opening, CO2 insertion and cyclic carbonate formation were illuminated explicitly through the of characteristic absorption peaks changing, which further providing direct and visual evidence for the mechanism proposing. This study has important theoretical significance for the comprehensive utilization of environmental pollutants and energy. [ABSTRACT FROM AUTHOR]

Two mononuclear ruthenium(II) complexes based on dianionic {N4} ligands and with axial pyridines have been prepared and characterized crystallographically (1) or by 2D NMR spectroscopy using residual dipolar couplings (2). The {N4} ligands provide a constrained equatorial coordination with one large N−Ru−N angle, and additional non‐coordinating N atoms in case of 2. Their redox properties have been investigated (spectro)electrochemically, and their potential to serve as water oxidation catalysts has been probed using cerium ammonium nitrate (CAN) at pH 1.0. Complex 1 undergoes rapid degradation, likely via ligand oxidation, whereas 2 is more rugged and exhibits 80 % efficiency in the CeIV‐driven water oxidation, with a high initial turnover frequency (TOFi) of 3.07×10−2 s−1 (at 100 equiv. CAN). The initial rate of O2 evolution exhibits 1st order dependence on catalyst concentration, suggesting a water nucleophilic attack mechanism. Repeated addition of CAN and control experiments show that high ionic strength conditions (both NO3− and CeIII) significantly decrease the TOF. [ABSTRACT FROM AUTHOR]

A perceived drawback of ruthenium(II) polypyridyl photosensitizers for phototherapeutic applications is their inadequate absorption in the visible region. Ru(II) dyads attached to light‐harvesting organic chromophores are studied to address this issue. Biotin‐appended compounds having one chromophore, namely BODIPY (boron‐dipyrromethene) (1) and Ru(II)‐(tpy)2 (2), or a dyad system containing BODIPY linked to Ru(II)‐(tpy)2 via a diphenylacetylene linker (3) were prepared and studied as photodetection agent and photosensitizes for Photodynamic Therapy (PDT) applications. The bichromophoric 3 with a strong absorption profile (ϵ≈71000 M−1 cm−1 at λmax=503 nm) and high singlet oxygen quantum yield (ΦΔ=0.63 in DMSO) was studied for PDT activity. This complex produced a superoxide anion radical via type‐I and singlet oxygen via type‐II photosensitization processes on light exposure, as evidenced from DNA photo‐cleavage experiments and in vitro DCFDA assay using reactive oxygen species scavengers/quenchers. Dyad 3 displayed an apoptotic photo‐cytotoxic effect against HeLa and H1299 cancer cells with a photocytotoxicity index (PI) value of >625 in HeLa cells with a PDT efficacy much superior to those of its monochromophoric analogs 1 and 2. The intrinsic emission of complex 3, utilized for cellular imaging, showed selectivity towards lysosomes. Finally, the remarkable potential of complex 3 was evidenced using a clinically relevant 3D multicellular tumor spheroid model. [ABSTRACT FROM AUTHOR]

Ferrocene‐based multidentate ligands have been widely used as metalloligands in crystal engineering because they self‐assemble into mixed‐metal complexes with various transition‐metal salts. In the present study, the ferrocene‐based ligand 1,2‐di(4‐pyridylthio)ferrocene (LFc) was complexed with dinuclear arene ruthenium building blocks [(p‐cymene)2Ru2(μ‐L)](OTf)2 to form the following trinuclear complexes with triangular structures: [(p‐cymene)2Ru2(μ‐L)(μ‐LFc)](OTf)2 [L=5,8‐dioxido‐1,4‐naphtoquinonato (1 a), 2,3‐dichloro‐5,8‐dioxido‐1,4‐naphtoquinonato (1 b), 2,5‐dioxido‐1,4‐benzoquinonato (2 a), 2,5‐dichloro‐3,6‐dioxido‐1,4‐benzoquinonato (2 b), and oxalato (3): OTf=trifluoromethanesulfonate]. A similar complexation of the ferrocene‐based ligand with [(p‐cymene)2Ru2Cl4] afforded a V‐shaped trinuclear complex [(p‐cymene)2Ru2Cl4(μ‐LFc)] (4). This study reveals the crystal structure and electronic states of 1–4. The absorption wavelengths and redox potentials of the trinuclear complexes depended on the type of L. [ABSTRACT FROM AUTHOR]

Molecular wheels composed of edge‐shared metal‐ligand coordination octahedra usually feature metal ions that are linked by bridging ligands possessing the same type of donor atoms. Herein we describe heterobridged wheels {Run(μ‐SR)n(μ‐X)n}(CO)2n (R=Trip; n=6, X=Cl, Br; n=8, X=I), which were formed in the reactions between Ru3(CO)12, 2,4,6‐triisopropylbenzenethiol (HSTrip) and HX (X=Cl, Br) or I2. These hexa‐ and octanuclear heterobridged wheels featuring thiolate/halide mixed bridging ligands have all been characterized by X‐ray crystallography as well as spectroscopic means including NMR, IR and ESI‐MS. [ABSTRACT FROM AUTHOR]

A ruthenium complex bearing an o‐benzoquinone dioximate dianion was isolated, and its ligand‐based redox chemistry was clarified. The reaction of [Cp*RuCl2(NO)] (Cp*=η5‐C5Me5) with o‐benzoquinone dioxime (LredH2) in the presence of a base afforded a dioximato ruthenium complex [Cp*Ru(NO)(Lred)] (1). Upon treatment with an iodonium salt, 1 underwent two‐electron oxidation of Lred along with ligand exchange to give the o‐dinitrosobenzene (Lox) iodido complex [Cp*RuI(Lox)] (2). 1H NMR, IR, X‐ray analyses, and DFT calculations revealed that the Lred ligand in 1 was oxidized and aromatized during the ligand substitution. The Lox ligand in 2 was reduced by benzensulfohydroxamic acid with the aid of a base, leading to regeneration of the Lred nitrosyl complex 1. The non‐innocence of Lred/ox in the ligand exchange would lead to level the energy profile of redox processes including catalysis. [ABSTRACT FROM AUTHOR]

A series of ligands containing a 1,4‐disubstituted 1,2,3‐triazole unit have been used for the formation of triple‐stranded dinuclear Ru(II) complexes. In contrast to the previously reported complexes of labile metals, the use of inert Ru(II) enabled stereoisomeric mixtures of triple‐stranded diruthenium(II) complexes to be accessed. The chromatographic resolution of the enantiomers of a reported helicate containing a more rigid 1,4‐xylyl spacer was carried out on cellulose. The ligand spacer was modified and as the flexibility increased the production of isomeric mixtures was detected; the mesocate and helicate forms were separated when an n‐propyl spacer was used. This pair of diastereomers was found to exhibit photoconversion, a unique observation for Ru(II) compounds of this type. Partial separation via chromatographic resolution was achieved for compounds containing an n‐butyl spacer, and the presence of a mesocate/helicate pair confirmed. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of Ru3(μ‐CO)3(CO)5‐type cluster complexes bound to a dinucleating PNNP 'expanded pincer' ligand. Each bidentate PN pocket of the ligand chelates a single ruthenium center of the cluster and can undergo deprotonation concomitant with dearomatization of its naphthyridine core. Although the cluster bearing a partially dearomatized ligand reacts with H2, we found no indication that this proceeds via a pathway involving metal‐ligand cooperativity. [ABSTRACT FROM AUTHOR]

The synthesis of the unsymmetric macrocyclic tetrakismidazolium salts H4‐4(PF6)4 and H4‐5(PF6)4 featuring a 2,6‐pyridinylene‐ and a 2‐bromo‐1,3‐xylylene‐bridged bisimidazolium unit is described. Reaction of macrocycle H4‐4(PF6)4 with Ag2O yields the tetranuclear complex [6](PF6)4 composed of four AgI ions sandwiched in between two tetra‐NHC ligands. The 2,6‐pyridinylene‐bridged bisimidazolium moiety of the macrocycles can be site‐selectively deprotonated and metallated with RuII or RhI to give the pincer complexes [8](PF6)3‐[11](PF6)3. Introduction of a second metal in these complexes by deprotonation/metallation and oxidative addition to the 2‐bromo‐1,3‐xylylene‐bridged bisimidazolium moiety of the macrocycles proved not possible. [ABSTRACT FROM AUTHOR]

Heterometallic μ‐nitrido complexes have been synthesized from organometallic complexes containing O/S‐donor ligands and a ruthenium(VI) nitride. The treatment of [Ir(tpip)(L)2] (tpip−=[N(Ph2PO)2]−; L=cyclooctene (coe) or 2,6‐dimethylphenylisocyanide (xylNC)) and [Ir{N(iPr2PS)2}(coe)] with [Ru(LOEt)(N)Cl2] (LOEt−=[Co(η5‐C5H5){P(O)(OEt)2}3]−) (1) afforded [(L)(tpip)Ir(μ‐N)Ru(LOEt)Cl2] (L=coe (2) or xylNC (3)) and [(coe){N(iPr2PS)2}Ir(μ‐N)Ru(LOEt)Cl2] (4), respectively, in which the Ir−N(nitride) bonds show double bond character. The bonding in 2–4 can be described by two resonance forms: Ir(I)−N≡Ru(VI) and Ir(III)=N=Ru(IV). The treatment of [Ph4P][Ir(CO)2Cl2] with 1 afforded (PPh4)[(CO)Cl2Ir(μ‐N)Ru(LOEt)Cl2] (5) that reacted with [Tl(SR)] to give (PPh4)[(CO)(RS)2Ir(μ‐N)Ru(LOEt)Cl2] (R=xyl (6), C6F4H (7)). The reaction of [M(acac)(CO)2)] or [Ru(acac)2(coe)2] (acac−=acetylacetonate) with 1 gave [(CO)(acac)M(μ‐N)Ru(LOEt)Cl2] [M=Ir (8), Rh (9)] or [(H2O)(acac)2Ru(μ‐N)Ru(LOEt)Cl2] (10), whereas the treatment of [Ru(acac)2(MeCN)2] with 1‐azidoadamantane (AdN3) yielded a Ru(II) tetrazene complex, [Ru(acac)2(N4Ad2)] (11). [ABSTRACT FROM AUTHOR]

This study describes the synthesis and characterization of the photoluminescent and water‐soluble complex cis‐[Ru(phen)2(2Apy)]2+ (Ru2Apy, phen=1,10‐phenanthroline and 2Apy=2‐aminopyridine), which exhibits spectroscopic and physicochemical properties favorable for biological applications. 1H‐NMR, photoluminescence, and UV‐vis spectroscopy experiments show bidentate coordination of the 2Apy ligand, which leads to a blue shift in the emission spectrum and places the 3MLCT in proximity to the 3MC excited states, thus enabling a photochemical pathway. Under continuous light irradiation at 450 nm, Ru2Apy opens the coordinating site of the NH2 group in 2Apy to form the monoacetonitrile complex cis‐[Ru(phen)2(2Apy)(CH3CN))2+, with a quantum yield of 0.457. Further irradiation leads to a second photoprocess to form the bis‐acetonitrile cis‐[Ru(phen)2(CH3CN)2]2+ complex, with a quantum yield of 0.002. Ru2Apy binds to human serum albumin via non‐covalent interactions with Kb=4.63×10−9 mol L−1, ΔH=−3.4×10−3 kcal mol−1, and ΔS=8.7 kcal mol−1K−1, and displays a moderate inhibition of AChE with an IC50 of 13.2±2.0 μmol L−1. The complex also exhibited high uptake into HeLa cells with no cytotoxicity. Furthermore, the emissive response of Ru2Apy was be used to assess, in real‐time, the aggregation of Aβ1–40 in a dose‐dependent manner. [ABSTRACT FROM AUTHOR]

Amide synthesis is one of the most crucial transformations in chemistry and biology. Among various catalytic systems, N‐heterocyclic carbene (NHC)‐based ruthenium (Ru) catalyst systems have been proven to be active for direct synthesis of amides by sustainable acceptorless dehydrogenative Coupling of primary alcohols with amines. Most often, these catalytic systems usually use monodentate NHC and thus require an additional ligand to obtain high reactivity and selectivity. In this work, a series of cationic Ru(II)(η6‐p‐cymene) complexes with thioether‐functionalized N‐heterocyclic carbene ligands (imidazole and benzimidazole‐based) have been prepared and fully characterized. These complexes have then been used in the amidation reaction and the most promising one (i. e. 3 c) has been applied on a large range of substrates. High conversions albeit with moderate yields have generally been obtained. [ABSTRACT FROM AUTHOR]

A new method to synthesize complexes of the type [(CNC)RuII(NN)L]n+ has been introduced, where CNC is a tridentate pincer composed of two (benz)imidazole derived NHC rings and a pyridyl ring, NN is a bidentate aromatic diimine ligand, L=bromide or acetonitrile, and n=1 or 2. Following this new method a series of six new complexes has been synthesized and characterized by spectroscopic, analytic, crystallographic, and computational methods. Their electrochemical properties have been studied via cyclic voltammetry under both N2 and CO2 atmospheres. Photocatalytic reduction of CO2 to CO was performed using these complexes both in the presence (sensitized) and absence (self‐sensitized) of an external photosensitizer. This study evaluates the effect of different CNC, NN, and L ligands in sensitized and self‐sensitized photocatalysis. Catalysts bearing the benzimidazole derived CNC pincer show much better activity for both sensitized and self‐sensitized photocatalysis as compared to catalysts bearing the imidazole derived CNC pincer. Furthermore, self‐sensitized photocatalysis requires a diimine ligand for CO2 reduction with catalyst 2ACN being the most active catalyst in this series with TON=85 and TOF=22 h−1 with an electron donating 4,4′‐dimethyl‐2,2′‐bipyridyl (dmb) ligand and a benzimidazole derived CNC pincer. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of the 15N‐labeled analogue of the mitochondrial calcium uptake inhibitor [Cl(NH3)4Ru(μ‐N)Ru(NH3)4Cl]3+ (Ru265) bearing [15N]NH3 ligands is reported. Using [1H,15N] HSQC NMR spectroscopy, the rate constants for the axial chlorido ligand aquation of [15N]Ru265 in pH 7.4 buffer at 25 °C were found to be k1=(3.43±0.03)×10−4 s−1 and k2=(4.03±0.09)×10−3 s−1. The reactivity of [15N]Ru265 towards biologically relevant small molecules was also assessed via this method, revealing that this complex can form coordination bonds to anionic oxygen and sulfur donors. Time‐based studies on these ligand‐binding reactions reveal this process to be slow relative to the time required for the complex to inhibit mitochondrial calcium uptake, suggesting that hydrogen‐bonding interactions, rather than the formation of coordination bonds, may play a more significant role in mediating the inhibitory properties of this complex. [ABSTRACT FROM AUTHOR]

The thermal and photochemical reactivity of Ru(CO)3(dpae) (1) and Ru(CO)2(dpae)(PPh3) (2) towards H2 and diphenylacetylene is described. These reactions are monitored by NMR spectroscopy in conjunction with the parahydrogen induced polarisation (PHIP) effect, spatially resolved chemical shift imaging and the Only Parahydrogen Spectroscopy (OPSY) signal filtering method. The results are supported by DFT. The thermal and photochemical reactions of 1 with H2 proceed by CO loss and form Ru(H)2(CO)2(dpae) (3). 1 catalyses the formation of 1,2 diphenylethane, cis‐ and trans‐stilbene, and 1,2,3,4 tetraphenylbutadiene under 325 nm irradiation at 295 K in a reaction where Ru(CO)2(dpae)(η2‐CHPh=CPhCPh=CHPh) forms. When the same reaction is monitored under thermal conditions at 333 K the η2‐diene complex is no longer detected but hydride containing Ru(CHPhCH2Ph)(H)(CO)2(dpae) and Ru(CO)2(dpae)(trans‐stilbene) are seen. For 1, the photochemical promotion of hydrogenation through 325 nm irradiation results in an approximate 5.5‐fold increase in turnover at 333 K when compared to no irradiation. In contrast, 2 reacts thermally with H2 at 295 K through PPh3 and CO loss with both Ru(H)2(CO)(dpae)(solvent) and 3 being detected. Under irradiation, CO loss dominates and two isomers of Ru(H)2(CO)(dpae)(PPh3) form. While 2 forms the same 4 organic products at 295 K and a second isomer of Ru(CHPhCH2Ph)(H)(CO)2(dpae) alongside the diene complex no photochemical promotion of hydrogenation is observed. [ABSTRACT FROM AUTHOR]

The catalytic activity towards water oxidation of a strongly coupled bimetallic ruthenium complex, trans‐[Ru(tpy)(bpy)(μ‐CN)Ru(py)4(OH2)]3+ (RuIIRuIIOH2), where tpy=2,2′:6′,2"‐terpyridine, bpy=2,2′‐bipyridine and py=pyridine are presented. At pH 1 the first two oxidation reactions are centred at the aquo fragment and result in the RuIIRuIIIOH2 and RuIIRuIVO redox states as confirmed by its spectroscopy and DFT calculations. Oxidation by an additional electron is followed by an irreversible step and a catalytic wave associated with the water oxidation reaction. At pH 1 the reaction with an excess of Ce(IV) results in the generation of an stoichiometric amount of oxygen based on molar amounts of the added Ce(IV). The dominant species during the catalytic cycle is the three‐electron oxidized product, RuIIIRuIVO. The reduction of the concentration of Ce(IV) monitored at 370 nm follow the rate equation, −d[Ce(IV)]/dt=kox[Ce(IV)][RuIIRuIIOH2] with a kox=82±3 M−1s−1 at T=298 K. The RuIIIRuIVO species is not stable and reacts to give RuIIRuIVO. [ABSTRACT FROM AUTHOR]

Heteroleptic ruthenium (II) complexes featuring donor functionalized phenyl‐terpyridine (ph‐tpy) and a monocarboxylic‐(ph‐tpy)/(tpy) are synthesized and characterized. Reactions of ruthenium (II) precursors at 80 °C favored heteroleptic complexes formation over the homoleptic side products. Visible light excitation of these complexes resulted in the metal‐to‐ligand charge transfer (MLCT) transitions. The inter‐planar torsional angle between the atoms of donor functionalized phenyl ring and the central pyridine (py) of the tpy core strongly influences visible light absorption and photovoltaic properties. The lower inter‐ring py‐ph torsion in the acceptor end of the MLCT structures and its increase in the oxidized doublets could prevent the back electron transfer. The ruthenium atom and the acceptor functionalized tpy host the triplet‐MLCT spin density. Ambient temperature excited‐state decay followed the energy gap law and occurred in the order of a few nanoseconds. Herein, we evaluate the photosensitizing ability of these complexes via a combined experimental and computational approach. [ABSTRACT FROM AUTHOR]

The preparation and characterization of a new ruthenium nitrosyl based on the pentadentate ligand (CH2py)2Me[9]aneN3 (1‐methyl‐4,7‐bis(pyridin‐2‐ylmethyl)‐1,4,7‐triazacyclononane) is reported. The octahedral species contains a {RuNO}6 fragment and can be isolated in the solid state as a PF6− salt. In acetonitrile, this platform allows exploring the reduction processes in 1‐electron steps from {RuNO}6 to {RuNO}8, with associated E° values of 0.421 V and −0.628 V (vs. Ag/AgCl, 3 M NaCl), respectively. The {RuNO}7 species is paramagnetic, its EPR spectrum in vitrified acetonitrile at 90 K is consistent with an S=1/2 center with g=(2.0095, 1.9992, 1.8785) coupled to a 14N nucleus, with A=(6.9, 30.24, 1.85)×10−4 cm−1. In acidified aqueous solution, the first reduction process at 0.101 V leads to the formation of {RuNO}7, as in aprotic medium (acetonitrile). However, the incorporation of a second electron is coupled to a protonation process of the nitroxyl group, generating a coordinated azanone (HNO) compound with pKa(HNO)=11.0. Spectroscopic information obtained via spectroelectrochemistry and electronic structure calculations assist in the rationalization of results. Overall, this new compound enhances the library of nitrosylated Ru species with combined redox, acid‐base, and spectroscopic characterization in water and confirms experimental correlations found in related species. [ABSTRACT FROM AUTHOR]

The reaction of the known closo‐ruthenacarborane 3‐H‐3‐Cl‐3,3‐(PPh3)2‐closo‐3,1,2‐RuC2B9H11 with tridentade nitrogen‐based ligands of the general formula (C5NH4CH2)2NR (R=H, Me, Et, iPr, But) in benzene solution at 60 °C allowed us to isolate novel ruthenacarborane clusters 3,3,3‐(2'‐NC5H4CH2)2NR‐pseudocloso‐3,1,2‐RuC2B9H11. According to the performed X‐ray study, the obtained compounds are the first examples of pseudocloso‐metallacarboranes bearing unsubstituted C2B92−nido‐carborane ligand. In spite of the determined pseudocloso structure of the complexes in the solid state, the recorded 11B{1H} NMR spectra indicate that some of them are converted into the closo isomers in solution. The conducted quantum‐chemical calculations have confirmed the subtle difference between two configurations and possible rearrangement in solution. The performed electrochemical investigations show the ability of the formed ruthenacarboranes to undergo reversible oxidation to Ru(III) species. [ABSTRACT FROM AUTHOR]

A simple and efficient protocol allows the oxidation of the cyclopentadiene derivative 5H‐dibenzo[e,h]‐dibenzo[3,4 : 6,7]cyclohept[1,2‐a]azulene (CpCH) provide according ketone CpCO. Comparable to the situation found for CpCH, the bending of the four annulated six‐membered rings defines the C2 symmetric molecular structure of CpCO. The cyclopentadienone CpCO readily reacts with [Ru3(CO)12] and [Fe3(CO)12] to generate tricarbonyl complexes of the type [(η4‐CpCO)M(CO)3]. In contrast to [(η4‐CpCO)Ru(CO)3], the tricarbonyliron(0) complex is sensitive to oxygen and moisture. Refluxing [(η4‐CpCO)Ru(CO)3] in isopropanol makes the hydrido‐bridged complex [((η4‐CpCO)2H)Ru2(CO)4H] accessible, an analogue to Shvo's catalyst. Both ruthenium complexes and their ligand CpCO were characterized spectroscopically and by single crystal x‐ray diffraction. The activity of [(η4‐CpCO)Ru(CO)3] was investigated for a series of transfer hydrogenation reactions. [ABSTRACT FROM AUTHOR]

A series of new Ruthenium(II) complexes based on the (1,10‐phenanthrolin‐5‐yl)diethyl phosphonate ligand L2 and their corresponding phosphonic acid along with reference compounds are synthesized in order to evaluate the influence of the phosphonate substitution on the catalytic performance of such molecules. UV‐vis absorption and emission spectroscopy show, that introduction of a phosphonate moiety into the periphery of the phenanthroline ligand does not alter the photophysical properties of the complex. In contrast, the electrochemical features of all compounds are affected upon respective functionalization compared to the reference molecule [Ru(bpy)3](PF6)2 in aqueous medium. Photostability tests in water or in water/persulfate show a dependency of the stability towards photodecomposition on quenching efficiency with persulfate anion. The lower quenching efficiency thus leads to increased stability based on the negative charge of the phosphonate moiety in 2 and P1 in aqueous medium following a quenching efficiency trend of [Ru(bpy)3](PF6)2>1>2>P1. Photocatalytic water oxidation using [Ru(dpp)(pic)2](PF6)2 reveals that compound 1 and [Ru(bpy)3](PF6)2 doe not exhibit any activity under the utilized conditions, P1 shows a negligible TON of 7, whereas compound 2 reaches a TON of 140 after 1 h. This fact highlights that the redox potential is not the sole driver in the catalytic cycle and accentuates the importance of different criteria determining the suitability of photosensitizers in light‐driven water oxidation, such as light absorption, redox potential of the RuIII/RuII event, photostability towards and quenching efficiency with the sacrificial agent. [ABSTRACT FROM AUTHOR]

The preparation and characterization of a new ruthenium nitrosyl based on the pentadentate ligand (CH2py)2Me[9]aneN3 (1‐methyl‐4,7‐bis(pyridin‐2‐ylmethyl)‐1,4,7‐triazacyclononane) is reported. The octahedral species contains a {RuNO}6 fragment and can be isolated in the solid state as a PF6− salt. In acetonitrile, this platform allows exploring the reduction processes in 1‐electron steps from {RuNO}6 to {RuNO}8, with associated E° values of 0.421 V and −0.628 V (vs. Ag/AgCl, 3 M NaCl), respectively. The {RuNO}7 species is paramagnetic, its EPR spectrum in vitrified acetonitrile at 90 K is consistent with an S=1/2 center with g=(2.0095, 1.9992, 1.8785) coupled to a 14N nucleus, with A=(6.9, 30.24, 1.85)×10−4 cm−1. In acidified aqueous solution, the first reduction process at 0.101 V leads to the formation of {RuNO}7, as in aprotic medium (acetonitrile). However, the incorporation of a second electron is coupled to a protonation process of the nitroxyl group, generating a coordinated azanone (HNO) compound with pKa(HNO)=11.0. Spectroscopic information obtained via spectroelectrochemistry and electronic structure calculations assist in the rationalization of results. Overall, this new compound enhances the library of nitrosylated Ru species with combined redox, acid‐base, and spectroscopic characterization in water and confirms experimental correlations found in related species. [ABSTRACT FROM AUTHOR]

A new heteroleptic ruthenium complex based on a 2,2′;6′,2′′‐terpyridine (tpy) and a thioether‐based tridentate ligand, btap (btap: 2,6‐bis(2‐thioanisyl)pyridine) was synthesized. Under visible light irradiation, this complex in solution in acetonitrile undergoes a photochemical ejection of the thioether ligand leading to [Ru(tpy)CH3CN)3]2+ and the free ligand. The reaction was monitored using NMR and UV‐Vis spectroscopies. This is very probably the first example of a tridentate ligand being expelled by the action of light. [ABSTRACT FROM AUTHOR]

The multiredox reactivity of bioinorganic cofactors is often coupled to proton transfers. Here we investigate the structural, thermochemical, and electronic structure of ruthenium‐amino/amido complexes with multi‐ proton‐coupled electron transfer reactivity. The bis(amino)ruthenium(II) and bis(amido)ruthenium(IV) complexes [RuII(bpy)(en*)2]2+ (RuII‐H0) and [RuIV(bpy)(en*‐H2)2]2+ (RuIV‐H2) interconvert reversibly with the transfer of 2e−/2H+ (bpy=2,2'‐bipyridine, en*=2,3‐diamino‐2,3‐dimethylbutane). X‐ray structures allow correlations between the structural and electronic parameters, and the thermochemical data of the 2e−/2H+ multi‐square grid scheme. Redox potentials, acidity constants and DFT calculations reveal potential intermediates implicated in 2e−/2H+ reactivity with organic reagents in non‐protic solvents, which shows a strong inverted redox potential favoring 2e−/2H+ transfer. This is suggested to be an attractive system for potential one‐step (concerted) transfer of 2e−and 2H+ due to the small changes of the pseudo‐octahedral geometries and the absence of charge change, indicating a relatively small overall reorganization energy. [ABSTRACT FROM AUTHOR]